Vertical scaling of the epitaxial structure and lithographic lateral scaling are the traditional approaches used to improve transistor performance. Selective doping of the collector region is yet another approach used to improve the speed of operation of a transistor. For example, by minimizing the area of the extrinsic collector, through selective doping by ion implantation, we can realize reduced base collector capacitance (Cbc) and thus reduce the parasitic capacitance of a transistor. For this approach to be effective, the region surrounding the selectively doped region has to be resistive. This requires the elimination of charge at the interfaces of the re-grown layers and materials that constitute the transistors after implant for selective doping.
The primary objective of the work published in the literature up to now has been using in-situ atomic hydrogen cleaning at low temperature for the removal of oxygen and carbon between epitaxially grown layers. However, no information has been published on the preparation of InP surfaces for the purpose of reducing interface charge using in-situ atomic hydrogen cleaning. Additionally, the reason for the origin of charge at the InP epilayer/InP substrate is also not known. Novel methods for reducing interface charge between epitaxial layers grown before and after ion implantation for high-performance electronic devices that capitalize on the benefits of selective doping for reducing parasitics are disclosed in the present disclosure.
Among the variety of device combinations that have been used in Optoelectronic Integrated Circuit (OEIC) fabrication the simplest is an InP Single Heterojunction Bipolar Transistor (SHBT) approach in which the base-collector (B-C) junction is used as the absorption region of the p-i-n photodiode (PD) However, a pin photo diode and a SHBT in the OEIC disclosed in prior art are not capable of high performance for Ultra wideband applications because a photo absorbing layer of a pin photo diode and a collector layer of a SHBT typically have same doping and thickness.
An OEIC according to the present disclosure is capable of high performance and may be used in Ultra wideband applications.